The Astra 900's design was based on the German Mauser C/96 from World War I. Like the German Mauser, the Astra 900's wooden holster doubled as a detachable butt stock. It featured a 10-round stripper clip and fired 7.63 mm cartridges an approximate distance of 500 yards at a speed of 143 meters per second using a recoil/single firing system. The entire gun was considered inferior to German weapons, and most were modified to meet the Wehrmacht's standards.
Supplied to the German military as of March 1943, the Astra 900 did not see extensive service with the Wehrmacht, unlike other Astra models such as the Astra 300 and Astra 600. Little more than 1,050 Astra 900's were delivered for German use, and their manufacturing source, Astra-Unceta y Cia SA ceased production of this model in January 1944.